Conventionally, when a plate-shaped workpiece is formed into a desired curved shape by press-forming in order to manufacture a large-sized structure such as a LNG tank, for example, a workpiece formed with a press machine is taken out from the press machine and a wooden gauge, which has been prepared in advance, is fitted to the workpiece so as to examine its shape.
Then, when it is judged that the workpiece needs to be further forming-machined as a result of the shape examination by the wooden gauge, the workpiece is returned to the press machine so as to press the same further.
As mentioned above, in the conventional press-forming, it is necessary to prepare the wooden gauge in advance in order to examine the shape of the workpiece after forming. Particularly, when the workpiece needs to be formed in a complicated shape such as the LNG tank, the shape examination cannot be performed with one kind of wooden gauge and a plurality of kinds of wooden gauges need to be prepared in advance.
Also, when the workpiece is taken out once from the press machine so as to fit the wooden gauge thereto for examining the shape of the workpiece by the wooden gauge, there is a problem that work time is prolonged and work efficiency is deteriorated.
Moreover, there is also a problem that judgment of acceptance is difficult because the shape examination needs to be performed by fitting a curved surface of the wooden gauge to a curved surface of the workpiece.
Further, when the workpiece is large, it is not always easy to fit the wooden gauge to the workpiece in the first place.
Also, when a local deformation of the workpiece is caught in fitting the wooden gauge thereto, sometimes it is erroneously determined to be failure even though it is within the allowable range.
Note that, recently, the mixed reality (MR) technology that an image of a virtual space is superposed on an image of a real space at an optional viewpoint and a composite image obtained in this manner is presented to an observer is attracting attention as an image technology for seamlessly integrating the real world with the virtual world seamlessly in real time (Patent Documents 1-4).